Aerosol paints using conventional solvent reduced pigmented organic polymeric binders have found wide acceptance because of their ready availability to apply paint coatings without the comcomitant clean up problems associated with brushing applications and the brush-marks not found with spray coatings. Until recently, aerosol paints were conventionally water-free, solvent thinned products formulated with propellants of the fluorochloro hydrocarbon class. Concern over fluorinated hydrocarbon propellants in the atmosphere gave impetus to use of non-fluorinated or halogenated propellants, primarily low molecular weight hydrocarbons such as butane, propane, hexane, heptane, etc., which were flammable.
With the development of water-reducible paint systems characterized by ease of application, ready clean up, and freedom from fire hazard, water-containing systems in aerosol paints became of major interest. Water-containing aerosol spray paints have the advantage of low toxicity levels, noncombustible spray paint systems, and in some cases ready clean up with soap and water after completion of the paint application.
The following patents are of interest in the development of the aerosol paint art and the present invention.
Howard U.S. Pat. No. 4,187,204, takes advantage of resinous synthetic polymers or paint binders; illustratively, maleinized oils, oil modified alkyds, copolymer oils, epoxy resins, etc., having sufficient carboxyl groups (acid value) to be solubilized in water by neutralization of the acid groups present. Howard's products contained some water, generally less than 8%. Acid values of the resins were neutralized with ammonia and amines, and dissolved in water-soluble solvents. Howard includes the lower molecular weight hydrocarbons fluorocarbons, etc., CO.sub.2, nitrous oxide, cyclo-propane, etc. Among the host of non-distinguished propellants dimethyl ether was named. The water content was limited to less than 8% however.
U.S. Pat. No. 3,998,775 Taub is primarily related to water-in-oil type emulsion paints wherein the binder phase is a vinyl acetate acrylic copolymer containing a pigment in a liquid hydrocarbon component. A surfactant aids in stabilizing the emulsion formed.
Stern in U.S. Pat. No. 4,066,596 relates to a particular mechanical valve for dispensing aqueous acrylic latex emulsions.
Broadhead U.S. Pat. No. 2,985,602 teaches the concept of producing a low molecular weight alkyd resin having an acid value between 6 and 25 which is made water-dispersible by neutralization with lithium hydroxide.
U.S. Pat. No. 4,240,940 Vasishth et al. teaches an aerosol paint which is capable of being cleaned up with water containing from 8%, but preferably less than 1% of water in which the binder vehicle solids are a water-reducible alkyd resin dissolved in a solution of Butyl Cellosolve and n-butanol. Other solvents for the water-reducible alkyd are ethylene glycol monobutyl ether, Butyl Carbitol and V.M.&P. Naphtha.
U.S. Pat. No. 4,125,499 Howard uses organic co-solvents including acetone, ethers, ethylene glcyol n-butyl ether, etc. with about 5% of water with some water-soluble alkyd resins (Aquamac 1200, Kelsol 3902, etc.). Aliphatic hydrocarbons and halofluorocarbons and methyl ethers including dimethyl ether are used in propellant admixtures.
Suk U.S. Pat. No. 4,265,797 reduces an aerosol paint using up to 30% propellant which includes among the other water-miscible propellants, dimethyl ether. The resins disclosed appear to be very similar to Rohm & Haas U.S. Pat. No. 2,795,564.
Rotheim U.S. Pat. No. 1,892,750 teaches use of dimethyl ether among other propellants for dispensing a spray of liquid from a pressurized container.
Attention is also directed to a Suk Belgium Pat. No. 890,564 of Jan. 18, 1982 which contains from 10-50% water and from 0-50% dimethyl ether and another propellant in conjunction with up to 45% polar organic co-solvents in an aqueous aerosol paint system.